Structure, Vibrational Spectra and 11B‑NMR Chemical Shift of Na8[AlSiO4]6(B(OH)4)2: Comparison of Theory and Experiment
journal contributionposted on 06.09.2016 by Alexander G. Schneider, Lars Schomborg, Anna C. Ulpe, Claus H. Rüscher, Thomas Bredow
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Density functional theory (DFT) calculations at generalized gradient approximation (GGA) level were performed to interpret experimental IR and Raman vibrational spectra, to assign 11B-NMR chemical shifts, and to calculate the structure of the tetrahydroxyborate sodalite Na8[AlSiO4]6(B(OH)4)2. Full optimization of the intercalated compound gave the following structural parameters of B(OH)4–: B–O–B (105.3–115.3°) and B–O–H (111.5–115.4°) angles, B–O (1.476 Å, 1.491 Å) and O–H (0.98 Å) distances. The calculated normal modes were assigned to experimental IR and Raman spectra. In general, close agreement between theory and experiment was obtained. The mean absolute deviation (MAD) is below 11 cm–1. We also calculate the thermodynamical stability of Na8[AlSiO4]6(B(OH)4)2 with respect to Na8[AlSiO4]6(BH4)2 in the context of the tetrahydroborate hydration reaction.